Movable parts and their carriers on packaging machines are generally made of steel. Steel is suitable for both heated parts, for example welding systems for the plastic welding, and for non-heated parts, for example folding devices for folding boxes or carriers for folding devices.
The stiffness (elasticity module: 20.times.10.sup.10 N/m.sup.2) of steel speaks positively for its use in the manufacturing of a movable part or its carrier. Due to its relatively high values for the specific heat conductivity (15 to 45 W/m.multidot.K) and the specific heat capacity (0.4 to 0.5 kJ/kg.multidot.K), steel is used in welding units.
Steel has the disadvantage that it is relatively heavy (density: 6.3 to 8.1 kg/dm.sup.3), and thus relatively great masses must be accelerated in the packaging machines. This results in large-mass parts and carriers, for which high driving forces must be produced. The high moments of inertia of steel are also disadvantageous in high performance packaging machines, in which very high accelerations must occur.
Plastics as parts or carriers would indeed have low moments of inertia due to their relatively low densities, however, with reference to their stiffness they do not meet the demands made by movable parts or carriers. Plastics cannot be utilized for parts to be heated because of their comparatively low heat conductivity.
The basic purpose of the invention is to improve the movable parts or their carriers on a packaging machine with another material, whereby the material is intended to clearly have a lesser density than steel. The stiffness of the material must be sufficient. In addition, the material is intended to have very good values for the specific heat conductivity and the specific heat capacity in order to be able to use it also for parts to be heated, and to thus have to store only one single material for both parts to be heated and parts not to be heated.